JP2003228034A - Laser optical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a compact laser optical device in which a separation angle between a desired modulation beam and an unnecessary diffracted beam in a plurality of diffracted beams available by using an accoustooptical modulation element AOM is enlarged, and only the desired modulation beam is picked up. <P>SOLUTION: A light beam emitted from a laser light source 1 and made incident on the AOM2 is modulated by the AOM2, divided into a plurality of diffracted beams and emitted. An optical element 32 having a positive power is so arranged that the optical axis of the optical element coincides with the beam axis of the desired modulated beam. The beam axes of the respective diffracted beams emitted from the optical element 32 are once converged behind the focal point of the optical element 32, and further advances as a diverged light beam. Only the desired modulated beam is available by providing a shielding member 4 at a position which is sufficiently separated from the optical element 32. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acousto-optical element (hereinafter referred to as AO) as a beam intensity modulating means which can be used for laser markers, laser trimmers, laser displays and the like.
M)), or a beam scanning device in which a beam scanning mechanism is added to the device. Specifically, the desired modulated beam diffracted by the AOM,
Techniques for clearly separating other unnecessary diffracted beams and extracting only the desired modulated beam

[0002]

2. Description of the Related Art It is known that a laser device having various functions can be constructed by modulating a laser beam by AOM. The AOM can modulate the intensity of an incident beam and is used in various laser devices such as laser markers, laser trimmers, and laser displays. A laser intensity modulation system includes a direct modulation system, and a low output semiconductor laser often uses the direct modulation system. However, as the laser output increases, the duty ratio decreases in the direct modulation method. On the other hand, since the AOM can secure the duty ratio even when the laser beam power is large, it is an effective modulation means in a laser device using a watt class high power laser.

There are two diffracted beams emitted from the AOM, that is, the 0th order light and the 1st order light. However, depending on the incident conditions of the beam, the -1st order and + 2nd order diffracted lights may be emitted simultaneously. . Of these, normally, only the first-order diffracted light is used as the modulated light. This will be referred to as the desired modulated beam. Since other beams are unnecessary, they will be called unnecessary diffracted beams. It is necessary to block unnecessary diffracted beams. However, the diffraction separation angle of the diffracted beam emitted from the AOM is as small as several milliradians.
Therefore, it is difficult to shield only the unnecessary diffracted beam in the vicinity of the AOM, and if an attempt is made to shield a beam other than the desired modulated beam by a light blocking plate having an aperture, the beam diameter and the aperture diameter become substantially the same. Then, the beam is diffracted at the edge of the aperture. Further, if the positions of the openings are displaced, the amount of transmitted light is reduced, and the light utilization efficiency is reduced.

A technique for cutting off unnecessary diffracted beams and extracting only desired modulated beams has been disclosed in Japanese Patent Laid-Open No. 9-5689.
The technique described in the publication is known. This technology
A plurality of diffracted beams with a slight separation angle emitted from the AOM are guided to a beam expander consisting of a convex lens of two groups, and a shading plate with a pinhole is placed on the focal plane of the front group to achieve the desired modulation. Only the beam passes through.

[0005]

At a position sufficiently distant from the AOM, the separation distance of a plurality of diffracted beams emitted from the AOM is widened, so that unnecessary diffracted beams can be shielded easily, but a long optical path length is required. The device becomes large. As a workaround, it is possible to make the device smaller by folding the optical path back with a mirror, but the device configuration becomes complicated,
Adjustment is also complicated. As another method of the related art for increasing the separation distance of a plurality of diffracted beams, as shown in FIG.
There is a method of disposing a wedge substrate on the emission end side of the OM.
A plurality of diffracted lights 1, 2 incident from the surface of the wedge substrate 3
Is transmitted through a predetermined substrate thickness, reflected on the back surface of the wedge substrate 3, again transmitted through the substrate, and emitted from the front surface of the wedge substrate 3. The plurality of diffracted lights 1 and 2 that have been close to each other are separated to some extent by the above steps, and after the separation, the opening 4
Unnecessary diffracted beams can be shielded via the light shielding member 4 having a. However, with this method, astigmatism occurs in the beam and the condensing characteristics deteriorate. Further, since the optical path of the beam is folded back, the arrangement of the system becomes complicated when the beams of the three primary colors are combined in the latter stage of this system. Further, since the system needs to be installed for each optical path of the three primary colors, the system arrangement becomes more complicated. JP-A-9
The optical system described in Japanese Patent No. 5689 has an advantage that even a plurality of partially overlapping light beams can be clearly separated by a light shielding plate having a pinhole that allows only a desired beam to pass therethrough. However, since the focal points of the respective light fluxes are very close to each other, the tolerance given to the pinhole configuration is not so large. Ideally, it is desired that an aperture larger than the modulated beam diameter be used to shield unnecessary diffracted beams and that a long optical distance is not required.

In the laser device, it is desirable that the modulated beam is propagated in a parallel or nearly parallel state. When the beam diverges, the size of the rear optical system needs to be increased, which increases the cost. From the principle of the Gaussian propagation characteristics of the laser beam, it is known that increasing the beam diameter improves the parallelism of the propagating beam.
In applications such as a laser trimmer and a laser scan display, once the beam diameter is expanded, the depth of focus at the time of final focusing is shallow, and if the depth is shallow, the positional accuracy of the machined surface or screen becomes strict. From the above, it is rare that an optical system that increases the beam diameter to improve the parallelism of the propagating beam is adopted. In short, it is desirable to propagate the beam while maintaining a state as close as possible to the beam diameter emitted from the laser.

In a device that modulates and uses lasers of different wavelengths, the AOMs corresponding to the laser beams of different wavelengths have the same problem. The number of diffracted beams increases when each of the beams having different wavelengths passes through the AOM, and a method of efficiently blocking unnecessary diffracted beams among these beams at the same time is desired. Although the desired modulated beams selected by the light shielding means have different wavelengths, a device for condensing or scanning these beams is conceivable. In this case, it is desired to have an apparatus configuration capable of making the condensing positions and spot sizes of beams having different wavelengths coincide with each other.

In view of these problems, in the present invention, A
The main purpose is to block unnecessary diffracted beams emitted from the OM within a short optical path. The main purpose is to make it possible to control the parallelism of a desired modulated beam. Further, the purpose is as follows. It enhances the diffracted light separation effect and relaxes the processing accuracy of parts and the adjustment accuracy of assembly. In a laser device that simultaneously uses lasers having different wavelengths, all unnecessary diffracted beams are shielded at the same time, and a desired modulated beam is converted into a parallel beam. Modulated beams with different wavelengths are focused at the same focal point.
The beams having different wavelengths modulated by the AOM are scanned and focused at the same position, and the focused spot size is also made the same. It is an object of the present invention to provide a beam scanning device using these laser optical devices.

[0009]

In order to solve the above-mentioned problems, in the invention described in claim 1 of the present application, in a laser device having a light intensity modulating means by an acousto-optic modulator (hereinafter referred to as AOM), A plurality of diffracted beams emitted from the AOM are arranged with the optical axis of an optical element having negative power behind the AOM coaxially with the beam optical axis of a desired modulated beam emitted from the AOM. A light-shielding member having an opening of a size that enlarges the separation angle of the above and allows only the desired modulated beam to pass and does not allow the other unnecessary diffracted beam to pass, and the center of the opening is aligned with the optical axis. And blocking the unnecessary diffracted beam.

According to a second aspect of the invention, in the laser device having a light intensity modulation means by AOM, the AO
Behind M, the optical axis of the optical element having positive power is
It is arranged coaxially with the beam optical axis of the desired modulated beam emitted from the OM, and the beam optical axes of a plurality of unnecessary diffracted beams emitted from the AOM and having different emission angles are once converged behind the focal point of the optical element. At a point, the separation angle is expanded by diverging after intersecting the optical axis of the optical element, and the distance from the convergence point is equal to or greater than the distance from the optical element to the convergence point. , The unwanted diffracted beam is arranged by arranging a light shielding member having an opening having a size that allows only the desired modulated beam to pass and does not pass any other unnecessary diffracted beam so that the center of the opening coincides with the optical axis. It is characterized in that it is shielded from light.

According to a third aspect of the invention, in the laser device having a light intensity modulating means by AOM, the AO
Behind M, the optical axis of an afocal optical system composed of a second group lens having a positive power is arranged coaxially with the beam optical axis of a desired modulated beam emitted from the AOM, Due to the refraction of the front group of the system, the AO
Immediately before the rear group of the afocal optical system, the beam angles of a plurality of unnecessary diffracted beams emitted from M are converged and diverged once behind the focal point of the optical element to expand the separation angle. Alternatively, a light-shielding member having an opening of a size that allows only the desired modulated beam to pass therethrough and does not allow other unnecessary diffracted beams to pass at a position immediately after is disposed such that the center of the opening coincides with the optical axis. The feature is that unnecessary diffracted beams are shielded.

According to a fourth aspect of the invention, in the laser optical device according to the third aspect, the afocal optical system is a beam expander having a rear group focal length longer than a front group focal length. In a fifth aspect of the present invention, a plurality of laser beams having different wavelengths are individually modulated by corresponding AOMs, and among the obtained plurality of diffracted beams, beam optical axes of desired modulated beams are coaxially combined. A beam combining means composed of a plurality of deflecting devices, the combined beam including different wavelengths combined by the beam combining means is arranged behind the beam combining means so that the optical axis of the beam coincides with the optical axis of the achromatic lens. Incident on the afocal optical system composed of
Arranged immediately before or after the rear group of the afocal optical system, having an opening having a size that allows only the combined beam to pass and does not allow other unnecessary diffracted beams to pass, and the center of the opening is the optical axis. It is characterized in that only the desired modulated beam is extracted as a parallel light flux by the matching light shielding member.

According to a sixth aspect of the invention, in the laser optical device according to the fifth aspect, the corresponding A
By varying the carrier frequency of the ultrasonic waves input to the OM in accordance with the wavelength of the incident laser beam, the separation angles of the plurality of diffracted beams are made substantially equal to each other, and the beam combining means produces the desired modulated beam. The optical axes of the beams are combined coaxially, and the optical paths of the unnecessary diffracted beams are made to substantially coincide with each other. According to a seventh aspect of the invention, in the laser optical device according to the fifth or sixth aspect, an achromatic condensing lens is arranged behind the afocal optical system.

According to an eighth aspect of the invention, in the laser optical device according to the sixth or seventh aspect, among the beams incident on the afocal optical system, the beam having the longer wavelength has a shorter diameter. Is larger than the diameter of the beam. According to a ninth aspect of the invention, there is provided a beam scanning device including the laser optical device according to any one of the first to eighth aspects, wherein the desired modulated beam is scanned behind all the optical systems. A beam scanning device having one or two beam scanning means is provided.

[0015]

According to the first aspect of the present invention, the separation angle of a plurality of diffracted beams is expanded by the optical element having negative power, and only the desired modulated beam is extracted by the light shielding member. According to the second aspect of the invention, the separation angle of the plurality of diffracted beams is expanded by the optical element having a positive power, and only the desired modulated beam is extracted by the light shielding member. According to the third aspect of the present invention, the optical element having a positive power expands the separation angle of the plurality of diffracted beams, and the desired modulated beam that has passed through the aperture of the light blocking member is emitted even after being emitted from the afocal optical system. Beam parallelism is maintained.

According to the invention described in claim 4, the distance between the beam optical axis of the desired modulated beam and the beam optical axis of the unnecessary diffracted beam at the position of the light shielding member becomes larger. According to the invention described in claim 5, by making the beam optical axes of a plurality of desired modulated beams having different wavelengths coincide with each other, a difference in optical path due to a difference in wavelength does not occur. According to the invention of claim 6, the unnecessary diffracted beam does not cause a difference in optical path due to a difference in wavelength.

According to the invention described in claim 7, when applied to a beam scanning device or the like, a desired modulated beam focuses on a predetermined image plane position. According to the invention described in claim 8, when applied to a beam scanning device, desired modulated beams having different wavelengths are focused on a predetermined image plane position with the same spot size. A beam scanning device using each laser optical device can be provided.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram illustrating a first embodiment of the present invention. In FIG. 1, emitted from the laser light source 1,
The parallel beam incident on the AOM2 is modulated by the AOM2 and is emitted as a plurality of diffracted beams such as 0th order light and ± 1st order light. The plurality of diffracted beams emitted from the AOM 2 have a separation angle depending on the wavelength of the incident beam and the carrier frequency of the ultrasonic vibration input to the AOM.
Although the separation angle of the plurality of diffracted beams is small, by placing the optical element 31 having negative power immediately after that, the diffraction angle of the diffracted beam emitted from the optical element 31 is expanded at a short optical distance due to the refraction effect. it can. By arranging the optical element 31 so that its optical axis coincides with that of the desired modulated beam 5 to be used thereafter, the desired modulated beam 5 is obtained.
Passes through the center of the lens, its beam optical axis goes straight without being refracted. However, the desired modulated beam 5 incident as a parallel light flux is emitted as a divergent light flux. Optical element 3
Behind 1, the beam other than the desired beam, that is, the unnecessary diffracted beam 6 is sufficiently separated in distance from the desired modulated beam 5, and therefore the aperture 4a having an appropriate size is formed.
Only the unnecessary diffracted beam 6 can be easily blocked by the light blocking member 4 having. Here, the appropriate size of the aperture 4a is preferably larger than the desired diameter of the modulated beam for the reasons already described. However, it must be set so that unnecessary diffracted beams do not enter. The power of the optical element 31, the distance from the optical element 31 to the light shielding member 4, and the size of the opening 4a are set so that only a desired modulated beam can be obtained even if there are unavoidable variations in component accuracy and the like. Decide Here, the optical element may be a single lens or a compound lens composed of a plurality of lenses, as long as the purpose is met. The point is that it can be optically handled as one lens. The same applies to the following description.

FIG. 2 is a diagram for explaining a second embodiment of the present invention. The difference from FIG. 1 is that the optical element immediately after the AOM is an optical element 32 having a positive power. Figure 2
In, the beam optical axis of the unnecessary diffracted beam has a separation angle with respect to the desired modulated beam and seems to be divergent, but the individual beams are parallel light beams. Therefore, the beams refracted by the optical element are focused on positions on the focal plane of the optical element that do not coincide with each other. However, the beam optical axis of each beam converges slightly behind the focal position of the optical element and then diverges. Although the separation angle of each beam before entering the optical element 32 is small,
By increasing the lens power of, the separation angle of the diffracted beam can be expanded at a short optical distance. By matching the optical axis of the optical element 32 with the beam optical axis of the desired modulated beam 5 actually used, the beam optical axis of the desired modulated beam 5 goes straight without being affected by refraction. However, the desired modulated beam 5 that has entered the optical element 32 as a parallel light flux advances as a divergent light flux after passing the focal position of the optical element 32. The unnecessary diffracted beam 6 is also focused on the focal plane of the optical element 32 as described above, but its beam optical axis intersects the beam optical axis of the desired modulated beam behind the focal position. Behind the intersection of both beam optical axes, the beam optical axis of the unnecessary diffracted beam 6 is separated from the beam optical axis of the desired modulated beam 5 in terms of distance, so that the position of the light shielding member 4 is changed as in the first embodiment. Only the desired modulated beam can be extracted by selecting it. When the position of the light shielding member 4 is placed at a position close to the intersection of the two beam optical axes, the distance between the two beam optical axes becomes smaller than the distance between the two beam optical axes when entering the optical element 3. There is a possibility that it will end up. In order to prevent this problem from occurring, the position where the light blocking member 4 is placed needs to be separated from the intersection by at least the same distance as the distance from the optical element 32 to the intersection.

FIG. 3 is a diagram for explaining the third embodiment of the present invention. The difference from FIG. 2 is that the optical element 7 having a positive power is arranged behind the light shielding member 4, and
The point is that an afocal beam converter is formed in combination with 2. That is, they are coaxially arranged so that the focal position of the optical element 32 and the focal position of the optical element 7 coincide with each other. In FIG. 3, the desired modulated beam 5 which is a parallel light beam incident on the optical element 32 is the optical element 3
The light is converged to the focal position by 2 and travels as divergent light as it is, and then enters the optical element 7 after passing through the opening 4a of the light shielding member 4 arranged immediately before the optical element 7 which is the rear group of the beam converter. As described above, since the optical element 7 is confocal with the optical element 32, the desired modulated beam 5 becomes a parallel light flux again after passing through the optical element 7, and travels on the optical axis. In the figure, the position of the light shielding member 4 is set before the beam enters the optical element 7. However, if only the effect of shielding the unnecessary diffracted beam is considered, the beam is replaced by the optical element instead of the light shielding member 4. Immediately after the light is emitted, the light shielding member 4 ′ may be placed as shown by the dotted line in the figure. This is the same in all subsequent embodiments. In general, it is usual to block unnecessary light beams as early as possible to prevent unnecessary scattered light in the optical element. Although not shown, even if the optical element 7 having a positive power is placed immediately after the light blocking member 4 in the optical system of FIG. 1 to convert the divergent light flux from the optical element 31 into a parallel light flux, The same effect as the embodiment can be obtained. This configuration is shown in Figure 3.
There is an advantage that the optical path length can be shortened as compared with the above configuration.

FIG. 4 is a reference example showing that the present invention can be applied to a frequently used modulation method. In FIG. 4, the parallel beam emitted from the laser light source 1 is focused on the modulation position of the AOM 2 by the optical element 8 having a positive power. By doing so, the modulation speed can be increased, so this configuration is often used.
The light beam modulated by the AOM2 becomes a plurality of divergent diffracted beams and exits the AOM2. These light fluxes are returned to parallel light fluxes by the optical element 9 which also has positive power. That is, the optical element 8 and the optical element 9 also form an afocal system. As with the third embodiment, the light beam that has passed through the optical element 9 can be extracted as the parallel light beam only by the desired modulated beam 5 by the beam converter including the light shielding member 4 inside. However, since the light beam modulated by the AOM 2 has a divergence angle, if this angle is larger than the separation angle, the light beams partially overlap and cannot be separated by the light shielding member 4. Since the separation angle of the AOM2 is not so large originally, the distance between the optical element 8 and the AOM2 must be made sufficiently large in order to make the divergence angle of the light flux smaller than that, and there is a difficulty in downsizing the device.

FIG. 5 is a partially enlarged view for explaining a more preferable condition of the third embodiment. The beam converter is divided into a beam expander and a beam condenser depending on the magnitude relationship between the focal lengths of the front group and the rear group. In the present invention, both of them can be used in principle, but the configuration of the beam expander is more suitable only from the purpose of increasing the degree of separation. In FIG. 5, the focal lengths of the optical elements 3 and 7 of the afocal lens group forming the beam converter are f
1 and f2. Here, f1 <f2, that is, the focal length of the optical element of the rear group is made larger than that of the front group.
As a result, the light shielding member 4 arranged almost in close contact with the rear group.
At the position of, the axial distance between the beam optical axis of the desired modulated beam and the beam optical axis of the unnecessary diffracted beam is calculated as f2 / n from the axial distance of both beam optical axes before entering the optical element of the front group. f1
The ratio can be increased. However, this configuration is a beam expander, and the beam diameter of the outgoing beam is larger than that of the incident beam by the same ratio as described above. As already mentioned, it is not a good idea to make the beam diameter too large, so in consideration of other factors, f1,
Define f2.

FIG. 6 is a diagram for explaining the fourth embodiment of the present invention. In the figure, 1-1 and 1-2 are laser light sources having different wavelengths. The wavelengths of these emitted lights are assumed to be λ1 and λ2. The parallel beams emitted from the respective light sources are modulated by the corresponding AOMs 2-1 and 2-2, and each emits a plurality of diffracted beams. A
The plurality of diffracted beams of wavelength λ1 emitted from the OM2-1 are
The light is deflected by the total reflection mirror 10, which is the first deflection device. The plurality of diffracted beams having the wavelength λ2 emitted from the AOM 2-2 are deflected by a dichroic mirror that is a second deflecting device that transmits the wavelength λ1 and totally reflects the wavelength λ2. At this time, of the plurality of diffracted beams emitted from the AOM 2-1, the beam optical axis of the desired modulated beam 5-1 and among the plurality of diffracted beams emitted from the AOM 2-2, the desired modulated beam 5- The total reflection mirror 10 and the dichroic mirror 11 are arranged so that the optical axes of the two beams coincide with each other. As a result, a plurality of desired modulated beams having different wavelengths become as if they were one beam, and become the combined beam 52. Both mirrors 10, 1
The unnecessary diffracted beam 6 deflected by 1 travels through an optical path different from that of the combined beam 52.

Generally, it is premised that the laser beam emitted from the laser light source 1 has good parallelism, but it may become slightly divergent while passing through several optical systems. In that case, as shown by a chain double-dashed line in the figure, a collimating lens 92 having a weak positive power may be inserted before the afocal lens system, if necessary. The combined beam 52 and the unnecessary diffracted beam 6 are passed through an afocal system similar to that of the third embodiment, so that the combined beam 5 is generated by the light shielding member 4.
Only 2 can be taken out from the optical element 73. By the way, the synthetic beam 52 includes different wavelength components λ1 and λ2. Therefore, if a lens system including chromatic aberration is used as the optical element 32 or the optical element 7 as shown in FIG. 3, the combined beam emitted from the optical element 7 is parallel to both wavelengths due to the difference in the refractive index depending on the wavelength. The light flux cannot be aligned. Therefore, all the optical elements used here are composed of an achromatic lens system, that is, an achromatic lens system. As a result, the combined beam 52 that enters the optical element 33 and exits the optical element 73 becomes a parallel light beam regardless of the difference in wavelength. that's all,
In order to make it easier to understand, the case of two colors has been described,
Generally, three primary colors are generally used for applications such as a display, and it is clear that this embodiment can be applied to the case of three colors. However, in that case, the third wavelength is set to λ3.
Then, as the third deflecting device, a dichroic mirror or a bandpass filter that transmits λ1 and λ2 and totally reflects λ3 is used. Other configurations are clear from the figure. In the following figures, the description is made for the case of two colors, but it is premised on the configuration for three colors.

FIG. 7 is a diagram for explaining an example of controlling the unnecessary diffracted beam in the configuration of FIG. 6 so as to be easily processed. The diffraction angle of the beam diffracted by the AOM changes depending on the wavelength of the incident light beam. The ultrasonic vibration applied to the AOM
It is a composite of carrier waves and modulated waves for signals. The modulated wave is amplitude modulated and appears as a change in intensity of the modulated beam. The difference in the frequency of the carrier wave appears in the difference in the interval of the lattice fringes generated inside the AOM. As a result, the difference in the separation angle of the diffracted beam appears. In FIG. 6, when light beams of different wavelengths are modulated by the AOMs 2-1 and 2-2 using carrier waves of the same frequency, as shown in the figure, the optical paths of unnecessary diffracted beams have different separation angles depending on the wavelengths. After passing through the dichroic mirror 11, they pass through different optical paths. In FIG. 7, the frequencies of the carrier waves given to the AOMs 2-1 and 2-2 are made different, and as a result, the separation angles of the unnecessary diffracted beams are controlled to be substantially equal to each other. Accordingly, the AOM 2-2 and the AOM 2-1 via the total reflection mirror 10 are arranged optically symmetrical with respect to the dichroic mirror 11. As a result, the unnecessary diffracted beam 62 that has passed through the dichroic mirror 11 follows almost the same optical path although the wavelength is different. By doing so, the opening 4a of the light shielding member 4 can be set to the most efficient size.

FIG. 8 is a diagram showing a fifth embodiment of the present invention and shows an optical system applicable to a scanning device and the like. This is a structure in which an achromatic condensing lens system 12 having a positive power is further arranged behind the optical element 73 having the structure shown in FIG. Synthetic beam 5 including different wavelengths emitted from the optical element 73
2 is a parallel light beam, and the achromatic condensing lens system 12
Incident on. Therefore, the combined beam 52 is as if
It behaves as if it were a beam of three wavelengths, and since the light flux of any wavelength is focused on the focal position of the achromat condensing lens 12 system, there is no color shift when used in a display or the like.

Although there is no wavelength difference in the focal length of the achromatic condensing lens system 12, the spot diameter when focused is changed depending on the wavelength. The size of the spot diameter is proportional to the wavelength and the F value (aperture ratio, that is, focal length / beam diameter).
When the wavelength is long, the F value can be decreased by increasing the beam diameter, so that the integrated value of the wavelength and the F value can be made substantially the same by controlling the beam diameter. Based on the above principle, it is possible to make the focused spot diameters of the synthetic beams 52 having different wavelengths uniform. This effect is effective for laser scan display applications. As a specific configuration, whether to use laser light sources with different emission beam diameters,
Alternatively, although not shown, it can be achieved by inserting a beam expander or a beam condenser somewhere from a laser light source to a deflecting device such as a total reflection mirror or a dichroic mirror.

FIG. 9 is a diagram showing an example of the sixth embodiment of the present invention. In FIG. 9, reference numerals 13 and 14 denote beam scanning means. In the example of the figure, 13 is a rotary polygon mirror and 14 is a galvanometer mirror. The optical system for making the light beam incident on the beam scanning means has at least a part of any one of the optical systems shown in FIGS. FIG. 9 shows FIG.
The example is shown by directly applying the optical system shown in FIG.

In the example of FIG. 9, the polygon mirror 13 and the galvano mirror 14 are described as examples of the beam scanning means.
The reference numeral 13 may be a galvanometer mirror. Alternatively, reference numeral 14 may be a polygon mirror. In the configuration shown,
The polygon mirror 13 scans the modulated beam 5 in the horizontal direction on the paper surface, and the galvano mirror 14 scans in the vertical direction on the paper surface.
According to the configuration of FIG. 9, using two beam scanning means,
The modulated beam 52 is scanned biaxially, that is, two-dimensionally. However, if the surface to be scanned moves,
When it is not necessary to scan two-dimensionally, the scanning means is 1
Individuals are all right. Although not shown, if an f.theta. Lens used in an image forming apparatus or the like is used together and the optical system before and after the scanning means is adapted to it, it is possible to display an image without distortion on a flat display. Is.

As the beam scanning device, a laser marker,
A laser trimmer, a laser scan display, etc. are conceivable, but not limited to these. According to the device constituting means of the present invention, unnecessary beams can be easily shielded with a short optical path length. Since the desired modulated beam can pass through the aperture of the light shielding member having an aperture larger than the beam diameter, diffraction due to the aperture edge does not occur, so a spot without side lobes can be generated when the beam is focused. Can be formed. Furthermore, since it is possible to prevent an unnecessary beam from reaching the processing surface or the screen, it is possible to improve processing quality or image quality. Alternatively, since beams having different wavelengths can be focused at the same focal position, processing with different spot diameters can be performed without changing the position of the processing member. Alternatively, in a laser scan display that irradiates a beam spot of three colors on the screen, there is no difference in focus position shift or spot size due to wavelength that causes color shift.

[0031]

According to the invention of claim 1 or 2, the AO
Of a plurality of diffracted beams emitted from M, unnecessary diffracted beams can be shielded in a short optical path, and a device that does not include an unwanted component and that extracts only a desired modulated beam without light amount loss can be downsized. According to the invention of claims 3 to 4,
The divergent light beam when the desired modulated beam is separated from unnecessary diffracted light can be returned to a parallel light beam, and by increasing the degree of separation, the allowable error in terms of component accuracy and device assembly accuracy can be reduced. It can be greatly eased.

According to the fifth to sixth aspects of the invention, in the laser device which simultaneously uses lasers having different wavelengths, all of the unnecessary diffracted beams are simultaneously shielded by one light shielding member, and a plurality of desired wavelengths different from each other are desired. The modulated beam can be treated as if it were one beam as a combined beam.

According to the seventh aspect of the present invention, since the combined beams containing different wavelengths can be focused on the same position, no color shift occurs when used in a display or the like. According to the invention of claim 8, when the combined beam containing a plurality of wavelengths is condensed, the condensed spot diameters are the same even if the wavelengths are different, and when used for a display or the like, no color shift occurs. According to the invention of claim 9, a beam scanning device using at least a part of the optical system according to claims 1 to 8 can be obtained, so that the device can be downsized.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a second embodiment of the present invention.

FIG. 3 is a diagram illustrating a third embodiment of the present invention.

FIG. 4 is a diagram of a reference example showing that the present invention can be applied to a frequently used modulation method.

FIG. 5 is a partially enlarged view for explaining more preferable conditions of the third embodiment.

FIG. 6 is a diagram illustrating a fourth embodiment of the present invention.

FIG. 7 is a diagram illustrating an example of controlling unnecessary diffracted beams in the configuration of FIG. 6 so as to be easily processed.

FIG. 8 is a diagram showing a fifth embodiment of the present invention.

FIG. 9 is a diagram showing an example of a sixth embodiment of the present invention.

FIG. 10 is a reference diagram showing an example of a conventional technique for increasing the separation distance of a plurality of diffracted beams.

[Explanation of symbols]

1 laser light source 2 AOM 31, 32, 33 Optical element 4 Light-shielding member 5 desired modulated beam 52 synthetic beam 6 Unnecessary diffracted beam 7 Optical element 10 Total reflection mirror 11 dichroic mirror 12 Achromat condenser lens system 13, 14 Beam scanning means

Claims (9)

[Claims] 1. A laser device having a light intensity modulating means by an acousto-optic modulator, wherein an optical axis of an optical element having negative power behind the acousto-optic modulator is emitted from the acousto-optic modulator. Arranged coaxially with the beam optical axis of the modulated beam, expanding the separation angle of a plurality of diffracted beams emitted from the acousto-optic modulator with different emission angles from each other, and passing only the desired modulated beam, otherwise unnecessary A laser optical device, characterized in that a light shielding member having an opening of a size that does not allow the passage of a diffracted beam is arranged so that the center of the opening coincides with the optical axis to shield the unnecessary diffracted beam. 2. A laser device having a light intensity modulating means by an acousto-optic modulator, wherein the optical axis of an optical element having a positive power is emitted from the acousto-optic modulator behind the acousto-optic modulator. Is arranged coaxially with the beam optical axis of the modulated beam, and the beam optical axes of a plurality of unnecessary diffracted beams emitted from the acousto-optic modulator are different from each other at the convergence point behind the focal point of the optical element. The separation angle is expanded by intersecting with the optical axis of the optical element and then diverging, and the desired angle is set at a position distant from the convergence point by a distance equal to or greater than the distance from the optical element to the convergence point. A light blocking member having an opening having a size that allows only the modulated beam of the above to pass but does not allow the other unnecessary diffracted beam to pass, and the center of the opening is arranged to coincide with the optical axis. A laser optical apparatus characterized by shielding the folding beam. 3. A laser device having a light intensity modulating means by an acousto-optic modulator, wherein an optical axis of an afocal optical system composed of a second lens group having positive power is provided behind the acousto-optic modulator. Arranged coaxially with the beam optical axis of the desired modulated beam emitted from the acousto-optic modulator,
Due to the refraction action of the front group of the afocal optical system, the beam optical axes of a plurality of unnecessary diffracted beams emitted from the acousto-optic modulator are converged and diverged after the focal point of the optical element. By enlarging the separation angle by this, at the position immediately before or after the rear group of the afocal optical system, a light-shielding member having an opening of a size that allows only the desired modulated beam to pass and does not allow other unnecessary diffracted beams to pass A laser optical device, characterized in that the center of the opening is arranged so as to coincide with the optical axis to shield the unnecessary diffracted beam. 4. The laser optical device according to claim 3, wherein the afocal optical system is a beam expander having a rear group focal length longer than a front group focal length. 5. A plurality of laser beams having different wavelengths are individually modulated by corresponding acousto-optic modulators, and a plurality of desired modulated beams among the plurality of obtained diffracted beams are coaxially combined. Beam synthesizing means consisting of a deflecting device, and synthesized by the beam synthesizing means,
A synthetic beam containing different wavelengths is placed behind it,
The beam optical axis coincides with the optical axis and is made incident on an afocal optical system constituted by an achromat lens, and is placed just before or after the rear group of the afocal optical system, and only the combined beam is passed, and otherwise The laser optical device is characterized in that it has an opening of a size that does not allow the unnecessary diffracted beam to pass therethrough, and that only the desired modulated beam is extracted as a parallel light beam by a light blocking member whose center coincides with the optical axis. 6. The separation angles of a plurality of diffracted beams are made substantially equal to each other by making the carrier frequencies of the ultrasonic waves input to the corresponding acousto-optic modulators different according to the wavelength of the incident laser beam. 6. The laser optical device according to claim 5, wherein the beam combining means coaxially combines the beam optical axes of the desired modulated beams, and the optical paths of the unnecessary diffracted beams are substantially matched. 7. A laser optical device according to claim 5, wherein an achromatic condensing lens is arranged behind the afocal optical system. 8. The beam having a longer wavelength among the beams incident on the afocal optical system has a diameter larger than that of the beam having a shorter wavelength.
Alternatively, the laser optical device according to item 7. 9. A beam scanning device comprising the laser optical device according to claim 1, wherein one beam scanning device scans the desired modulated beam behind all the optical systems. A beam scanning device comprising two beam scanning means.